661668 has 24 divisors (see below), whose sum is σ = 1764672. Its totient is φ = 189024.

The previous prime is 661663. The next prime is 661673. The reversal of 661668 is 866166.

It is an interprime number because it is at equal distance from previous prime (661663) and next prime (661673).

It is not an unprimeable number, because it can be changed into a prime (661663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3855 + ... + 4022.

It is an arithmetic number, because the mean of its divisors is an integer number (73528).

2⁶⁶¹⁶⁶⁸ is an apocalyptic number.

It is an amenable number.

661668 is an abundant number, since it is smaller than the sum of its proper divisors (1103004).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661668 is a wasteful number, since it uses less digits than its factorization.

661668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7891 (or 7889 counting only the distinct ones).

The product of its digits is 10368, while the sum is 33.

The square root of 661668 is about 813.4297757029. The cubic root of 661668 is about 87.1391616150.

The spelling of 661668 in words is "six hundred sixty-one thousand, six hundred sixty-eight".